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Cameron, M. D.

Publications and source records attributed to Cameron, M. D..

7 recordsLinked to original sources

Pharmacological rescue of mitochondrial dysfunction, neurite degeneration, and premature death of ALS and AD iPSC-derived neurons

Mitochondrial (MT) dysfunction is a key driver of ALS pathology. Without a healthy MT system, motor neurons (MN) function at sub-optimal levels and die. In addition, other effects of ALS, like axon/dendrite degeneration, may occur from a pathophysiological cascade spurred by MT dysfunction. A phenotypic screen identified Dipyridamole (DPM), an FDA-approved and safe drug, as having extraordinary effects on ALS patient induced pluripotent stem cell (iPSC)-derived MNs. The drug prevented MT fragmentation, loss of MT content, impaired MT bioenergetics, axon/dendrite degeneration, and premature MN death, extending neuronal survival by more than fivefold. Importantly, its efficacy extended across iPSC-derived neurons representing two different familial forms of ALS (C9orf72, TDP43) and Alzheimers disease (PSEN1), implying broad neuroprotection across ALS forms and other neurodegenerative diseases. DPM increased MT respiration and pyruvate uptake in a mechanism requiring the Mitochondrial Pyruvate Carrier (MPC), mechanistically explaining its biological activities. Thus, DPM is a promising drug to repurpose or refine for treating neurodegenerative diseases or other diseases that would benefit by augmenting pyruvate uptake into MT. TeaserDipyridamole, an FDA-approved drug, restores mitochondrial function and protects neurons in ALS and Alzheimers disease.

neuroscience↗

Design of an orally bioavailable small molecule that modulates the microtubule-associated protein tau's pre-mRNA splicing

Frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) is caused by the aberrant alternative pre-mRNA splicing of microtubule-associated protein tau (MAPT) exon 10, the inclusion of which encodes for a toxic tau protein harboring four microtube domains (4R tau). Here, we describe the design of an RNA-targeted small molecule that thermodynamically stabilizes the structure of a pre-mRNA splicing regulator element in the MAPT pre-mRNA exon 10-intron junction to reduce the inclusion of exon 10 and hence 4R tau abundance. Structure-based drug design was used to obtain compounds that form a network of specific interactions to the RNA including multiple interactions between a one nucleotide A-bulge and the Hoogsteen face of a closing GC base pair, the latter of which was enabled by the design of base triple interactions. A battery of assays revealed that the compound binds the target in vitro and in cells and affects pre-mRNA splicing in various cellular models including primary neurons from a human tau (htau) knock-in mouse model. The orally bioavailable compound was administered per os (p.o.), where treatment diminished exon 10 inclusion, and reduced the 4R tau protein isoform. Further, the molecule mitigated cellular pathologies and behavioral phenotypes observed in the htau transgenic mouse model. This study provides a potentially general pipeline to design compounds that target RNAs and affect disease pathways and deliver compounds that have oral bioavailability and blood-brain barrier penetrance.

biochemistry↗

Triazole 187 is a biased KOR agonist that suppresses itch without sedation and induces anxiolytic-like behaviors in mice.

Kappa opioid receptor agonists are clinically used to treat pruritis and have therapeutic potential for the treatment of pain and neuropsychiatric disorders. We have previously shown that triazole 1.1 is a G protein signaling-biased KOR agonist, that can suppress itch without producing signs of sedation in mice. This profile was recapitulated in rats and non-human primates however, triazole 1.1 had limited potency as an antipruritic. Here we describe a more potent, G protein signaling-biased agonist, triazole 187. Triazole 187 is a potent antipruritic agent and does not decrease spontaneous locomotor activity; interestingly, it produces anxiolytic-like behaviors in mice, an effect not observed for triazole 1.1. In addition to curbing sedation, triazole 187 produces only mild diuresis, resulting in 30% of urine output induced by U50,488H at dose that is 188-fold the antipruritic potency dose. Compounds like triazole 187 may present a means to treat anxiety accompanied by persistent chronic itch while avoiding sedation and diuresis accompanied by typical KOR agonists. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/638680v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@17e9e6aorg.highwire.dtl.DTLVardef@1d27741org.highwire.dtl.DTLVardef@9389dcorg.highwire.dtl.DTLVardef@3fd825_HPS_FORMAT_FIGEXP M_FIG Graphic Abstract C_FIG

pharmacology and toxicology↗

Zika virus-induced fetal demise is driven by strain- and dose-specific RLR-driven activation of the interferon response in the decidua, placenta, and fetus in Ifnar1-/- mice.

Congenital Zika syndrome (CZS), the set of fetal and neonatal complications associated with Zika virus (ZIKV) infection in pregnancy, was first noted during the outbreak in the Americas in 2015-16. However, there was an unequal distribution of ZIKV cases and severe outcomes in all areas where ZIKV emerged in the Americas, demonstrating that the risk of CZS varied over space and time. Recently, we demonstrated that phenotypic heterogeneity existed between closely-related ZIKV strains. All ZIKV strains tested infected the placenta but varied in their capacity to cause overt fetal harm. Here, we further characterized the relative contributions of virus genotype and infecting dose of two phenotypically distinct ZIKV strains across multiple timepoints in gestation in pregnant mice that lack type-I interferon receptor function (Ifnar1-/-). To better understand the underlying causes of adverse fetal outcomes, we used RNA sequencing to compare ZIKV-infected and uninfected tissues. We found that ZIKV infection triggers retinoic acid-inducible gene I (RIG-I)-like receptor-mediated activation of the interferon response at the maternal-fetal interface. However, modest chemical inhibition of RIG-I activation in the decidua and placenta did not protect against fetal demise. Instead, the fetal interferon response was significantly associated with fetal demise. Together, these findings suggest that the response to ZIKV at the maternal-fetal interface can vary depending on the infecting ZIKV genotype and dose, and that the fetal immune response is an important mediator of fetal harm. IMPORTANCEPreviously, we used a mouse model of ZIKV infection during pregnancy to assess the pathogenic potential to the fetus of a panel of five, low-passage ZIKV strains representing the viral genetic diversity in the Americas. We found that phenotypic heterogeneity existed between these closely-related ZIKV strains. Here, we show that this heterogeneity is driven by retinoic acid-inducible gene I (RIG-I)-like receptor-mediated activation of the interferon response at the maternal-fetal interface. We used chemical inhibition of the RIG-I pathway and measured the transcriptional activity of interferon stimulated genes in fetuses to demonstrate that the fetal immune response may contribute to fetal demise.

microbiology↗

Development of Clinically Viable Non-Muscle Myosin II Small Molecule Inhibitors with Broad Therapeutic Potential

Non-muscle myosin II (NMII), a molecular motor that regulates critical processes such as cytokinesis and neuronal synaptic plasticity, has substantial therapeutic potential. However, translating this potential to in vivo use has been hampered by the lack of selective tools. The most prototypical non-selective inhibitor, blebbistatin inactivates both NMII and cardiac myosin II (CMII), a key regulator of heart function. Using rational drug design, we developed a series of NMII inhibitors that improve tolerability by selectively targeting NMII over CMII, including MT-228, which has excellent properties such as high brain penetration and efficacy in preclinical models of stimulant use disorder, which has no current FDA-approved therapies. The structure of MT-228 bound to myosin II provides insight into its 17-fold selectivity for NMII over CMII. MT-228s broad therapeutic window opens the door to new disease treatments and provides valuable tools for the scientific community, along with promising leads for future medication development. HighlightsO_LIResearch suggests numerous indications, from axon regeneration and cancer, would benefit from a small molecule inhibitor of non-muscle myosin II, a molecular motor that regulates the actin cytoskeleton. C_LIO_LICurrent chemical probe options are very limited and lack sufficient safety for in vivo C_LIO_LIstudies, which we show is primarily due to potent inhibition of cardiac myosin II. C_LIO_LIRational design that focused on improving target selectivity over the pan-myosin II inhibitor, blebbistatin, led to the identification of MT-228, a small molecule inhibitor with a wide therapeutic window. C_LIO_LIHigh-resolution structure of MT-228 bound to myosin II reveals that selectivity results from a different positioning compared to blebbistatin and an important sequence difference between cardiac and non-muscle myosin II in the inhibitor binding pocket. C_LIO_LIA single administration of MT-228 shows long-lasting efficacy in animal models of stimulant use disorder, a current unmet and rapidly escalating need with no FDA-approved treatments. C_LI

cell biology↗

Basolateral Amygdala Corticotrophin Releasing Factor Receptor 2 Interacts with Nonmuscle Myosin II to Destabilize Memory

Inhibiting the actin motor ATPase nonmuscle myosin II (NMII) with blebbistatin (Blebb) in the basolateral amgydala (BLA) depolymerizes actin, resulting in an immediate, retrieval-independent disruption of methamphetamine (METH)-associated memory. The effect is highly selective, as NMII inhibition has no effect in other relevant brain regions (e.g. dorsal hippocampus [dPHC], nucleus accumbens [NAc]), nor does it interfere with associations for other aversive or appetitive stimuli, including cocaine (COC). To investigate a potential source of this specificity, pharmacokinetic differences in METH and COC brain exposure were examined. Replicating METHs longer half-life with COC did not render the COC association susceptible to disruption by NMII inhibition. Therefore, transcriptional differences were next assessed. Comparative RNA-seq profiling in the BLA, dHPC and NAc following METH or COC conditioning identified crhr2, which encodes the corticotrophin releasing factor receptor 2 (CRF2), as uniquely upregulated by METH in the BLA. CRF2 antagonism with Astressin-2B (AS2B) had no effect on METH-associated memory after consolidation, allowing for determination of CRF2 influences on NMII-based susceptibility after METH conditioning. Pretreatment with AS2B occluded the ability of Blebb to disrupt an established METH-associated memory. Alternatively, the Blebb-induced, retrieval-independent memory disruption seen with METH was mimicked for COC when combined with CRF2 overexpression in the BLA and its ligand, UCN3 during conditioning. These results indicate that BLA CRF2 receptor activation during learning can prevent stabilization of the actin-myosin cytoskeleton supporting the memory, rendering it vulnerable to disruption via NMII inhibition. CRF2 represents an interesting target for BLA-dependent memory destabilization via downstream effects on NMII.

neuroscience↗

Discovery of a Novel, Selective and Short-Acting Skeletal Myosin II Inhibitor

Myosin IIs, actin-based motors that utilize the chemical energy of ATP to generate force, have potential as therapeutic targets. Their heavy chains differentiate the family into muscle (skeletal [SkMII], cardiac, smooth) and nonmuscle myosin IIs. Despite therapeutic potential for muscle disorders, no SkMII-specific inhibitor has been reported and characterized. Here we present the discovery, synthesis and characterization of "skeletostatins", novel derivatives of the pan-myosin II inhibitor blebbistatin, with selectivity within the myosin IIs for SkMII. In addition, the skeletostatins bear improved potency, solubility and photostability, without cytotoxicity. Based on its optimal in vitro profile, Skeletostatin 1s in vivo tolerability, efficacy and pharmacokinetics were determined. Skeletostatin 1 was well-tolerated in mice, impaired motor performance, and had an excellent muscle to plasma ratio. Skeletostatins are useful probes for basic research and a strong starting point for drug development.

pharmacology and toxicology↗